The study of biomass moisture content impact on the efficiency of a power-producing unit with a gasifierand the stirling engine

Abstract

The aim of this study is to determine the impact of wood chip fuel moisture content on the overall efficiency of the power-producing unit of a mobile chipper consisting of a gasifier, the Stirling engine and a container-dryer. Research of utilization efficiency of heat emissions of the Stirling engine in a container-dryer has been conducted. The container-dryer design for wood chip drying due to thermal emissions of the Stirling engine has been developed. A mathematical model of the autonomous power-producing unit of mobile chipper functioning with wood chip fuel was developed. In addition, the physical experiment was conducted to determine the actual moisture content of wood chips after drying due to thermal emissions of the Stirling engine. According to the results of the experiments we obtained regression equations of the efficiency of power-producing unit dependence on the initial moisture content of biofuels for two cases - with drying in the container-dryer and without drying. Drying of fire wood chips due to utilization of thermal emissions of the Stirling engine in a container-drier of a proposed design improves the efficiency of the power-producing unit. The reduction of the fuel wood relative moisture content from 47.5% to 37.5% increases the efficiency by 7.34%, while moisture reduction from 37.5% to 27.5% results in higher efficiency of only 4.37%, a further reduction in moisture from 27.5% to 17.5% results in higher efficiency of only 2.47%. Thus, the greatest positive effect of drying fire wood chips due to heat recovery of the Stirling engine emissions is observed when using fuel wood with high initial moisture content of more than 30%.